dbcve.org
Tew 827dru FirmwareOperating system · Trendnet

CVE-2021-20158

CRITICAL · 9.8 CVSS v3.1 Published 2021-12-30
Mitigation only
No fix yet — a mitigation exists. There is no fixed release. A documented workaround reduces exposure in the meantime.
See remediation →
100/100
Remediation priority · Urgent
Remotely reachable No privileges Zero-click

Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.

NVD · unedited
Trendnet AC2600 TEW-827DRU version 2.08B01 contains an authentication bypass vulnerability. It is possible for an unauthenticated, malicous actor to force the change of the admin password due to a hidden administrative command.

Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.

dbcve analysis · high confidence

The Trendnet TEW-827DRU router firmware 2.08B01 contains a hidden administrative command that can be invoked without authentication, allowing an unauthenticated attacker to bypass the login mechanism and force a change of the admin password. This grants the attacker full administrative control over the device.

MitigationApply vendor firmware update if available; if no update exists, disable remote administration interfaces, segment the device on a restricted VLAN, or replace the device.

Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.

Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.

NVD · CPE data
Tew 827dru FirmwareOperating system
Affected:= 2.08b01

CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.

From the vector
Attack vector
Network
Complexity
Low
Privileges
None
User interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
High

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.

dbcve checks

Work through these to decide whether this CVE applies to you.

  1. Identify the installed firmware version
    Access the router's web administration interface and navigate to System > Firmware Upgrade or Status page, or use the command line (telnet/ssh if enabled) to run 'cat /proc/version' or 'nvram get firmversion'. Alternatively, check the bootloader or backup config file for version strings.
    Affected if The firmware version is exactly 2.08B01 (note: 'b' may be lowercase in some displays). Versions other than 2.08B01 are not affected by this specific CVE.
  2. Verify if remote web management is enabled
    Log into the router admin interface and check under System Administration > Remote Management or similar. Look for settings that allow HTTP/HTTPS access from WAN (Internet) ports. Use 'grep -i remote /etc/config/*' or inspect the NVRAM configuration via command line if available.
    Affected if Remote management is enabled on WAN interface. The vulnerability can be exploited remotely ONLY if remote administration is exposed to the internet (or an attacker on the same network if LAN-based exploitation is also possible).
  3. Confirm the device model is TEW-827DRU
    Check the device label on the physical router, the web interface System Status page, or the bootloader/serial output for the exact model number. Do not confuse with similar Trendnet models.
    Affected if The device is specifically the Trendnet TEW-827DRU model running firmware 2.08B01.
  4. Inspect for unusual hidden command endpoints (optional)
    If you have access to the firmware filesystem (via extraction or debug mode), search for undocumented CGI or API handlers in /www or /cgi-bin directories. Look for hardcoded credentials, backdoor paths, or password change functions that lack authentication checks.
    Affected if A hidden or undocumented administrative command handler exists in the firmware that does not validate session authentication before processing administrative actions.

You are affected if your Trendnet TEW-827DRU router runs firmware version 2.08B01 AND remote administration is accessible (either from WAN or an untrusted network segment).

Generated from the published advisory. Verify against your own configuration.

Check your environment

Paste your version and any relevant configuration and it will be compared against the affected criteria above. Do not include secrets or credentials.

AI-assisted, checked against the advisory. Informational, not a guarantee.

Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.

From vendor data
Mitigation available No clean upgrade yet — mitigate in the meantime
Mitigation

Apply vendor firmware update if available; if no update exists, disable remote administration interfaces, segment the device on a restricted VLAN, or replace the device.

Fix this in Tew 827dru Firmware Scoped from the published advisory
  • Consultation2.0 h
  • Implementation1.0 h
  • Testing1.0 h
  • Review / QA1.0 h
5.0 hours of engineering $910
Get help mitigating

An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $1,456.

Scan for this in your stack

Free · runs locally
dbcve dependency scanner

Check whether your project pulls in CVE-2021-20158 — or any other known-vulnerable package — straight from your lock files. Free and open source; it runs locally and uploads nothing.

Get it on GitHub Scan in the browser

References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2021-20158 in production — separate from our analysis above.

No notes yet

Be the first to add a field note for this CVE — a mitigation you’ve verified, a version caveat, or a link to a working fix. Sign in above to contribute.

What this is

A place for practitioners to share what actually worked: a mitigation you’ve tested, a configuration change, a version- or environment-specific caveat, or a link to a verified patch. The most useful notes rise to the top as peers upvote them, so the signal stays high.

What belongs here
  • Verified mitigations, workarounds, and config changes
  • Version or environment caveats, and links to real fixes
  • No weaponised exploit code, or anything meant to cause harm
  • No spam, self-promotion, credentials, or personal data